1. Field of the Invention
This invention relates generally to a hollow-fiber permeability apparatus, and more particularly to a hollow-fiber permeability apparatus in which a permeating region of a housing contains a bundle of hollow fibers, and materials can selectively permeate through the membranes formed by the permeable walls of the hollow fibers, between a fluid flowing along the exteriors of the hollow fibers, and another fluid flowing along the interiors of the hollow fibers. The permeation may be based on the principles of osmosis, dialysis, ultrafiltration, reverse osmosis or the like.
2. Description of the Prior Art
For example, a conventional hollow-fiber permeability apparatus is used for hemodialyzer in which toxic materials are removed from the blood of a patient suffering from renal failure or medicinal poisoning. Such apparatus is also used as an artificial lung, in which oxygen and carbon dioxide are exchanged with each other to increase the blood oxygen content. Further, it is used for purification or desalination of water in a reverse osmosis apparatus.
Accordingly, this invention can be most suitably applied to osmosis apparatus, dialysis apparatus, ultrafiltration apparatus and reverse osmosis apparatus, or to combinations of them in which a relatively large effective surface area of membrane is desired for the volume.
In the hemodialyzer metabolic wastes or excess ions permeate through the wall membranes from the blood of a patient to dialysate, and necessary ions permeate through the wall membranes from the dialysate to the blood, on the basis of Donnan's membrane equilibrium due to the concentration differences between the blood and the dialysate, and water is removed from the blood by ultrafiltration.
The conventional hemodialyzers are generally classified into coil-type, plate-type and hollow-fiber type. These types have merits and demerits, respectively.
FIG. 1 shows one example of the conventional hollow-fiber hemodialyzer. In this apparatus 10, the hollow fibers 5 are fixed at the upper and lower end portions of the housing 1 with polyurethane. The cut ends of the hollow fibers 5 are open to compartments formed by upper and lower covers of the housing 1.
Blood 36 from the artery of the patient during dialysis is introduced into the housing 1 through a blood inlet tube 14. While the blood 36 flows through the interiors of the hollow fibers 5, dialysis is effected between the blood 36 and dialysate 35 which flows along the exteriors of the hollow fibers 5. Metabolic wastes such as urea, uric acid and creatinine are removed from the blood 36. The purified blood 36 is discharged through the blood outlet tube 15 from the housing 1, and returned to the vein of the patient. During dialysis, water can be removed from the blood 36 by ultrafiltration. The hollow fibers used in the hemodialyzer as above described provide a relative large effective surface area of membrane for the size of the apparatus. Therefore, the dialyzer of this type can be smaller than the conventional coil-type, or Kiil-type dialyzer. Thus, the blood priming volume of the hollow-fiber dialyzer can be smaller, which is beneficial to the patient during dialysis. The dialyzer is also easier to handle.
Since the hollow-fiber type hemodialyzer has many merits, however, the dialyzer has the following demerits:
As shown in FIG. 1, thousands of the hollow fibers 5 are closely bundled in the permeating region of the cylindrical housing 1. It is difficult that the dialysate 35 can be perfused uniformly through the whole part of the bundle 6. The dialysate 35 flows mainly around the peripheral region of the bundle 6 adjacent to the inner wall of the housing 1, and the dialysis performance is extermely low in the central region of the bundle 6. Most of the housings of the marketted hollow-fiber type dialyzers are cylindrical in shape. The chlindrical housing may be ideal from the viewpoint of the simplicity of construction and of the facility of assembling. However, since numerous hollow fibers, for example, ten thousand hollow fibers are closely bundled in the permeating region, it is impossible to remove the disadvantage that the dialysate cannot be perfused through the central portion of the hollow-fiber bundle. If the diameter of the cylindrical housing is reduced to one third in order to perfuse the central portion of the hollow-fiber bundle with the dialysate, the length of the permeating region, namely that of the hollow fibers should be lengthened three times to maintain the same total membrane area of the hollow fibers. Such an apparatus is not only inconvenient for handling, but also it imposes high pressure loss on the blood introduced.
New types of the dialyzers are disclosed in Japanese Patent Opening Nos. 33888/1977 and 58079/1977 which were filed on Sept. 11, 1975 in Sweden and on Nov. 5, 1975 in U.S.A. respectively. In these dialyzers, the interior of the housing is partitioned into more than two compartments by walls. The compartments each are packed with hollow fiber bundles. Dialysate is introduced from the inlet tube formed at the lower end of the housing, flows up through the first compartment counter-currently to the blood, then it turns at the upper end portion of the compartment to flow down through the second compartment. The dialysate again turns at the lower end portion of the second compartment to flow up through the third compartment. Thus, the dialysate flows up and down in the housing. It is finally discharged from the outlet tube formed at the upper end of the housing. In such apparatus, the dialysate is contaminated with materials from blood after being perfused in the first compartment and further the contaminated dialysate flows through the second, and much more contaminated one flows in the third . . . compartments and so on.
In another example of the above-described patent openings, the dialysate is first perfused upward counter-currently to the blood in the first compartment, then it turns at the upper end portion of the first compartment to flow down through a first channelling route. The dialysate is again perfused upward counter-currently to the blood in the second compartment, and so forth. Therefore, the second and third compartments are perfused with the contaminated dialysate after the first and second compartments perfused, respectively. Accordingly, the apparatus of the above-described patent openings have the demerit that the total dialysis efficiency is deteriorated.
This inventor already proposed a novel hollow-fiber permeability apparatus in the U.S. Pat. No. 4,082,670, issued Apr. 4, 1978 in which the cross section of the permeating region of the housing is flattened or oblong, and dialysate flows uniformly through the whole hollow-fiber bundle counter-currently to the flow of blood, whereby the dialysis efficiency can be improved.
Since then, this inventor has further studied the proposed apparatus, and has invented a further improved hollow-fiber permeability apparatus.